Friedrich MWM09Y1J Service & Parts Manual page 35

OPERATION
9-12k Sequence of Operation
Overheating Control
Heat Pump Only
During heating operation, the signals being sent from the indoor unit allow the operating frequency limitation and prevent abnormal
high pressure. (The signal from the indoor unit must be divided as follows.)
1.Conditions for Start Controlling
Judge the controlling start with the indoor heat exchanger temperature after 2 seconds from operation start.
2.Control in Each Zone
The heat exchange intermediate temperature of indoor unit controls the following.
Defrost Control
Heat Pump Only
Defrosting is carried out by the cooling cycle (reverse cycle). The defrosting time or outdoor heat exchanger temperature is dependent
on specific conditions being met or satisfied before releasing defrost.
1.Conditions for Starting Defrost
The starting conditions must be made with the outdoor ambient air sensor (outdoor air temperature) and indoor coil sensor
(heat exchanger temperature). When the system is in heating operation for 6 minutes after the compressor is started or more than 45
minutes of accumulated time has passed since he start of operation or ending the defrost cycle
2.Conditions for Canceling Defrost
Current indoor coil sensor (heat exchanger temperature) is between 39°F~72°F)
35
Heat exchanger
thermistor temperature
Frequency
0Hz
50sec.
ON
Compressor
OFF
ON
Four way valve
OFF
ON
Fan
OFF
450pps
Electronic expansion
valve opening
Stop zone
Dropping zone
Keep zone
Up zone
Reset zone
60sec.
600sec. 50sec.
5sec.
350pps 450pps
PI control
5sec.
Initial opening